Light-emitting diodes (LEDs) can generally provide light in a more efficient manner than incandescent and/or fluorescent light sources. The relatively high power efficiency associated with LEDs has created an interest in using LEDs to displace conventional light sources in a variety of lighting applications. For example, in some instances LEDs are being used as traffic lights and to illuminate cell phone keypads and displays.
Typically, an LED is formed of multiple layers, with at least some of the layers being formed of different materials. In general, the materials and thicknesses selected for the layers influence the wavelength(s) of light emitted by the LED. In addition, the chemical composition of the layers can be selected to promote isolation of injected electrical charge carriers into regions (e.g., quantum wells) for relatively efficient conversion to light. Generally, the layers on one side of the junction where a quantum well is grown are doped with donor atoms that result in high electron concentration (such layers are commonly referred to as n-type layers), and the layers on the opposite side are doped with acceptor atoms that result in a relatively high hole concentration (such layers are commonly referred to as p-type layers).
LEDs also generally include contact structures (also referred to as electrical contact structures or electrodes), which are conductive features of the device that may be electrically connected to a power source. The power source can provide electrical current to the device via the contact structures. For example, the contact structures can deliver current along the lengths of structures to the surface of the device within which light may be generated.
Light-emitting devices may also include a wavelength-converting region, which can include, for example, one or more phosphor materials. The wavelength-converting material (e.g., phosphor) may be in the form of, for example, particles distributed in a second material (e.g., an encapsulant or adhesive, such as epoxy) to form a composite structure. Regions comprising wavelength-converting materials can absorb light having a first wavelength from a light-generating region (e.g., semiconductor region within an LED) and emit light having a second, different wavelength. As a result, a light-emitting device incorporating a wavelength-converting region can emit light having wavelength(s) that may not be possible to produce using LEDs without such regions.